[TS/JS] New gen TS code gen (#6302)

[TS/JS] New gen TS code gen (#6302)

* TS/ES6 modules spike iteration 1

* Initial modularized dasherized output

* Remove obsoleted parts and namespace wrapping

* Use _flatbuffers_ prefix

* First part of imports logic

* Second part of imports logic

* Fix TS/JS code removal mixup

* Alias imported symbols if same name from different namespaces and some fixes

* Use star import for bare imports

* Fix messed up string concat

* var to const and remove not needed semi

* Remove some cases of ns prefixing

* Add missing space

* Cleanups

* Completed initial import tracking logic

* Compilable output

* Adjust TypeScriptTest and dependents to work

* Use local flatbuffers package for tests

* Refactor away use of any

* Remove obsolete imported_fileset and reexport_map

* Still need any and fix JavaScriptTest.sh

* Fix test runs out of the box

* Temp add generated files

* TypeScriptTest replaces JavaScriptTest and cleanups

* Also remove reference to JavaScriptTest in TestAll.sh

* Remove old generated ts/js files

* Remove use of --js in generate_code scripts

* idl_gen_js_ts to idl_gen_ts and removal of js gen

* Remove obsoleted options

* Fix obsolete ts test detection

* Tweak ts compilation be as strict as possible

* Remove jsdoc type annotation generation

* Generated test ts files

* Fix search and replace messup

* Regenerated ts test output

* Use CharToLower

* Use normal for loop

* Rework namespacedir

* Revert "Rework namespacedir"

This reverts commit 6f4eb0104ceeb86011bb076ebca901138c48e068.

* Revert "Use normal for loop"

This reverts commit 676b2135bfaa1853dfbb06c92b5c16a0d81bb13a.

* Revert "Use CharToLower"

This reverts commit 2d08648d0d72d0af201fad80d54cdc76412b35e9.

* Again do rework but correct

* Avoid runtime cast

* Fix test runs

* Also add npm install to get tsc

* Bump node test versions

* for range to std for loop

* Clang format

* Missed one clang format

* Move accessor to later

* Attempt to make windows version of TypeScriptTest

* Want to see the output

* Try to get newer node at appveyor

* Style changes